operator==, !=, <, <=, >, >=(std::variant)

 

C++

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Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

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Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Library feature-test macros
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
integer_sequence (C++14)
Relational operators (deprecated in C++20)
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Comparisons (C++20)
strong_order weak_order partial_order strong_equal weak_equal	strong_ordering weak_ordering partial_ordering strong_equality weak_equality	is_eqis_neqis_ltis_lteqis_gtis_gteq
common_comparison_category
Common vocabulary types
pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
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to_chars (C++17)
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chars_format (C++17)
Type operations
declval (C++11)
as_const (C++17)
launder (C++17)

 

std::variant

Member functions

variant::variant

variant::~variant

variant::operator=

Observers

variant::index

variant::valueless_by_exception

Modifiers

variant::emplace

variant::swap

Non-member functions

visit

holds_alternative

get

get_if

operator==operator!=operator<operator<=operator>operator>=

swap

Helper classes

monostate

bad_variant_access

variant_size

variant_alternative

hash

Helper objects

variant_npos

 

Defined in header <variant>
template <class... Types> constexpr bool operator==(const std::variant<Types...>& v, const std::variant<Types...>& w);	(1)	(since C++17)
template <class... Types> constexpr bool operator!=(const std::variant<Types...>& v, const std::variant<Types...>& w);	(2)	(since C++17)
template <class... Types> constexpr bool operator<(const std::variant<Types...>& v, const std::variant<Types...>& w);	(3)	(since C++17)
template <class... Types> constexpr bool operator>(const std::variant<Types...>& v, const std::variant<Types...>& w);	(4)	(since C++17)
template <class... Types> constexpr bool operator<=(const std::variant<Types...>& v, const std::variant<Types...>& w);	(5)	(since C++17)
template <class... Types> constexpr bool operator>=(const std::variant<Types...>& v, const std::variant<Types...>& w);	(6)	(since C++17)

1) Equality operator for variants:

• If v.index() != w.index(), returns false;
• otherwise if v.valueless_by_exception(), returns true;
• otherwise returns std::get<v.index()>(v) == std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) == std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.

2) Inequality operator for variants:

• If v.index() != w.index(), returns true;
• otherwise if v.valueless_by_exception(), returns false;
• otherwise returns std::get<v.index()>(v) != std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) != std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.

3) Less-than operator for variants:

• If w.valueless_by_exception(), returns false;
• otherwise if v.valueless_by_exception(), returns true;
• otherwise if v.index() < w.index(), returns true;
• otherwise if v.index() > w.index(), returns false;
• otherwise returns std::get<v.index()>(v) < std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) < std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.

4) Greater-than operator for variants:

• If v.valueless_by_exception(), returns false;
• otherwise if w.valueless_by_exception(), returns true;
• otherwise if v.index() > w.index(), returns true;
• otherwise if v.index() < w.index(), returns false;
• otherwise returns std::get<v.index()>(v) > std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) > std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.

5) Less-equal operator for variants:

• If v.valueless_by_exception(), returns true;
• otherwise if w.valueless_by_exception(), returns false;
• otherwise if v.index() < w.index(), returns true;
• otherwise if v.index() > w.index(), returns false;
• otherwise returns std::get<v.index()>(v) <= std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) <= std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.

6) Greater-equal operator for variants:

• If w.valueless_by_exception(), returns true;
• otherwise if v.valueless_by_exception(), returns false;
• otherwise if v.index() > w.index(), returns true;
• otherwise if v.index() < w.index(), returns false;
• otherwise std::get<v.index()>(v) >= std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) >= std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.

Parameters

v,w

-

variants to compare

Return value

The boolean result of the comparison as described above.

See also

operator==operator!=operator<operator<=operator>operator>= (C++17)

compares optional objects (function template)